JNCC Report No. 423 Broad-scale biotope mapping of potential reefs in the Irish Sea (north-west of Anglesey) V. Blyth-Skyrme, C. Lindenbaum, E. Verling, K. Van Landeghem, K. Robinson, A. Mackie & T. Darbyshire October 2008 © JNCC, Peterborough 2008 ISSN 0963-8091 For further information please contact: Joint Nature Conservation Committee Monkstone House City Road Peterborough Cambridgeshire PE1 1JY Email: [email protected] Tel: +44 (0)1733 866905 Fax: +44 (0)1733 555948 Website: www.jncc.gov.uk This report should be cited as: Blyth-Skyrme, V., Lindenbaum, C., Verling, E., Van Landeghem, K., Robinson, K., Mackie, A., Darbyshire, T. 2008. Broad-scale biotope mapping of potential reefs in the Irish Sea (north-west of Anglesey) JNCC Report No. 423 Abbreviations BGS British Geological Survey CCW Countryside Council for Wales JNCC Joint Nature Conservation Committee MI Marine Institute NMW Amgueddfa Cymru - National Museum Wales SAC Special Area of Conservation UCC University College Cork Broad-scale biotope mapping of potential reefs in the Irish Sea (north-west of Anglesey) Contents Executive Summary.................................................................................................................1 1. Introduction.....................................................................................................................3 1.1 Background to study ................................................................................................3 1.2 Background to approaches in seabed habitat mapping............................................5 1.3 Survey Areas............................................................................................................7 1.3.1 Location .......................................................................................................7 1.3.2 Physical environment...................................................................................8 1.3.3 Biology.......................................................................................................10 1.4 Objectives ..............................................................................................................12 2. Methodology ..................................................................................................................14 2.1 Survey strategy and vessel.....................................................................................14 2.2 Navigation..............................................................................................................15 2.3 Acoustic data collection.........................................................................................15 2.3.1 Multibeam..................................................................................................15 2.3.2 Single-beam ...............................................................................................15 2.4 Seabed sampling....................................................................................................15 2.4.1 Selection of sampling stations ...................................................................15 2.4.2 Grab samples..............................................................................................16 2.4.3 Video samples............................................................................................16 2.5 Data processing and analysis .................................................................................18 2.5.1 Multibeam bathymetry and backscatter.....................................................18 2.5.2 Grabs Samples: Particle size analysis........................................................24 2.5.3 Samples: Biology.......................................................................................26 2.5.4 Video..........................................................................................................28 2.6 Data integration and presentation ..........................................................................30 3. Results ............................................................................................................................31 3.1 Multibeam bathymetry and backscatter.................................................................31 3.1.1 Area 1.........................................................................................................31 3.1.2 Area 2.........................................................................................................37 3.1.3 Area 3.........................................................................................................42 3.1.4 Area 4.........................................................................................................47 3.2 Sediment sample analyses......................................................................................52 3.2.1 Relationship between sediment and backscatter........................................57 3.3 Grab samples..........................................................................................................58 3.3.1 Infauna .......................................................................................................58 3.3.2 Infaunal assemblages .................................................................................61 3.3.3 Infaunal biotopes........................................................................................64 3.3.4 Comparison with data collected during the HABMAP project .................64 3.3.5 Epifauna .....................................................................................................68 3.4 Video analysis........................................................................................................70 3.4.1 Epifaunal assemblages...............................................................................70 3.4.2 Epifaunal biotope assignment....................................................................74 3.4.3 Epifaunal biotope descriptions...................................................................75 3.4.4 Epifaunal biotope distribution....................................................................96 3.5 Presence and distribution of Annex I reef habitat................................................100 4. Integrated assessment.................................................................................................107 4.1 Area 1...................................................................................................................107 Broad-scale biotope mapping of potential reefs in the Irish Sea (north-west of Anglesey) 4.2 Area 2...................................................................................................................109 4.3 Area 3...................................................................................................................111 4.4 Area 4...................................................................................................................113 5. Areas of conservation interest....................................................................................116 6. Summary and conclusions..........................................................................................117 6.1 Overview of results..............................................................................................117 6.2 Interpretation of acoustic data..............................................................................117 6.3 Interpretation of biological data...........................................................................117 6.4 Relationship between acoustic and biological data .............................................119 6.5 Identification of Annex I habitats ........................................................................119 6.6 Quality issues with the results..............................................................................120 6.7 General conclusions.............................................................................................121 7. Acknowledgements .....................................................................................................122 8. References....................................................................................................................124 9. Appendices...................................................................................................................129 9.1 Video log sheet ....................................................................................................129 9.2 Results of PSA from Emu....................................................................................130 9.3 Particle Size Analyses – Statistical methods .......................................................136 9.4 SACFOR abundance scale...................................................................................138 9.5 Full PSA sample statistics including laser diffraction results..............................139 9.6 Grab sample data (infauna)..................................................................................143 9.7 List of Biotope Codes used within this project....................................................163 9.8 Grab sample data (epifauna) ................................................................................164 9.9 Video analysis data ..............................................................................................169 Broad-scale biotope mapping of potential reefs in the Irish Sea (north-west of Anglesey) Executive Summary